Features of Cyclic Extrusion Compression: Method, Structure & Materials Properties

The Cyclic Extrusion Compression (CEC) is one of the methods of severe plastic deformation (SPD), used for producing nanomaterials. The CEC method allows materials to be deformed to arbitrarily large strains without changing the initial shape of sample. Large hydrostatic compressive stresses are exerted during deformation avoiding sample cracking. Using the CEC method Cu and aluminum alloys nanomaterials were produced. It has been found that, after exerting true strain of about ϕ = 14, only some part of the sample changes into a nanomaterial, while the remainder volume still shows the ultrafine microstructure. The nanometric microstructure is created generally inside the areas of intersecting microbands. Large misorientation has been found between the microbands and the surrounding material, facilitating the formation of nanograin boundaries. The hardness of samples increases with the increase of deformation, however only to a boundary level of about 100 MPa. The stabilization of hardening, above a deformation of about ϕ = 4, suggests the activation of softening processes. Independently to the stabilization of properties, the refinement of nanograins is continued, indicating the development of anomalies in the hardening – grain size relationship.